John Carmichael wrote:
The design which worked the best was a 1/8 inch spherical bead, suspended
by
thin brass crosswires, in the exact center of a 1/4 inch round hole. (The
style was about 24 inches from the analemma).
A very curious thing happens with this type of style. The bead alone,
Hello All,
The discussion about 'shadow sharpeners' is interesting.
When diffraction was mentioned I wondered if
a 'double-slit' diffraction apparatus and the resulting
interference pattern could be used as (or with) a vernier
scale to further increase resolution...
I'll have to play with
On Wed, 5 May 1999, Phil Pappas wrote:
Hello dialists:
I conducted over thirty different experiments using all sorts of hole,
crosshair and bead diameters. The objective, of course, was to find the
style which cast the smallest point of light or shadow onto the analemma.
The design
This subject seems to have strayed. Let us bring it back to the
shadows, where it belongs. In some countries they drive on the right.
In others they drive on the left. In the sunny Mediterranean island of
Malta, where I lived for a couple of years, they drive in the shade.
--
Frank Evans
Hello dialists:
Three years ago I built an equitorial interactive mechanical
heliochronometer of brass and wood based on the design described in chapter
xII, pgs. 193-202 of the Mayall's book. The heliochronometer consists of
four basic parts: base, dial plate, alidade or sighting instrument,
Patrick Powers wrote:
It is simply the pin hole camera effect again. Light passing through any
small aperture is focused . As the hole's size is changed the focusing
parameters are changed too. So with a fixed distance from hole to plate
there will be one size that works. A different size
I've put a picture of what I think is a sun tracking device on my web page at
linux.bbn.com/~koolish. If anybody has seen one or knows how it was used, let
me know. There are no markings on it.
Mike,
It would be fair to tell us which week, so that tourists would know when
to avoid the aulde countrie when scheduling visits.
Somehow I've lost the connection to the moving shadow edge. Except
for...
The only vehicular direction that seems to relate to the edge of the
moving shadow is
Troy contributed:
I've heard of at least one European country that made the switch from
left to right (though I forget which one), the switch took a 10 year plan.
Possibly the one which swapped around mid-day some years ago - can't
remember which? All traffic stopped for five minutes,
